Trialkylamine oxides are made by reacting trialkylamines with hydrogen peroxide. They are useful for many purposes such as in hair conditioners and shampoos as described in U.S. Pat. No. 3,086,943. When a C.sub.10-16 alkyl dimethylamine oxide as described in U.S. Pat. No. 3,086,943 is made, the products will gel if the concentration of the amine oxide exceeds about 30 weight percent. Alkyl dimethylamine oxides are described in Kirk-Othmer "Encyclopedia of Chemical Technology", 3rd Ed. At page 266, Kirk-Othmer states that "when a strictly aqueous system is employed, final concentrations of amine oxide should be limited to below 35% since higher concentrations tend to gel and prevent good mixing."
Hoh et al., J. Am. Oil Chem. Soc., 40 (1963) page 268-271 describe the synthesis of dimethyl dodecylamine oxide by reaction of dimethyl dodecylamine with 35% aqueous hydrogen peroxide. The product is a 30-40 weight percent aqueous solution of the amine oxide. Hoh et al. note that even using 35% aqueous hydrogen peroxide, the reaction mixture will gel unless diluted with water during the reaction.
Hoh et al. attempted to make dimethyl dodecylamine oxide without co-feeding water starting with 35%, 70% and 90% aqueous hydrogen peroxide. With 35% and 70% hydrogen peroxide, the product was a gel that could not be stirred. The reaction with 90% hydrogen peroxide was not completed because of darkening of the reaction mixture.
Chadwick U.S. Pat. No. 3,215,741 describes the preparation of di-C.sub.1-2 alkyl C.sub.10-20 alkylamine oxides by reaction of the tert-amine with hydrogen peroxide. While attempting to make the desirable concentrated solutions of the amine oxide, Chadwick found that when commercially available hydrogen peroxide containing 20-90 weight percent H.sub.2 O.sub.2 was used, the reaction sets up to a gel resembling a thick starch paste long before completion of the reaction. Chadwick's solution to the problem was to co-feed at least 20% hydrogen peroxide and sufficient water to the tert-amine such that the final product was water diluted. When dimethyl dodecylamine was used the most concentrated amine oxide solution that could be obtained was only 30-40 weight percent amine oxide.
A need exists for a solid non-hygroscopic flakeable trialkylamine oxide. Such materials would be useful as fabric softeners in laundry detergents. Statioraitis et al. U.S. Pat. No. 3,776,959 describes a process for making a solution of various amine oxides in a non-polar solvent such as toluene by dissolving a tert-amine in the non-polar solvent and adding aqueous hydrogen peroxide while removing water by azeotropic distillation. The product is a solution in an organic solvent. Such solutions could not be used in dry solid laundry detergent formulations.